Friday, March 8, 2013

Global temperatures are at a 4,000-year high

The news lately has been so full of broken weather records, it’s easy to just glaze over. But today we have one worth paying attention to: Mean global temperatures are warmer now than they have been at any time during the past 4,000 years.
A new study in the journal Science paints the clearest picture yet of the climate since the last ice age ended.
The researchers combined the results of 73 scientific studies that together pinpointed historical weather conditions, using analyses of sediment samples and ice cores and other methods, back 11,300 years. The result was a new hockey-stick graph, reinforcing the data in the old hockey-stick graph, as we noted yesterday.

After the ice age, [the researchers] found, global average temperatures rose until they reached a plateau between 7550 and 3550 bc. Then a long-term cooling trend set in, reaching its lowest temperature extreme between ad 1450 and 1850.
Since then, temperatures have been increasing at a dramatic clip: from the first decade of the twentieth century to now, global average temperatures rose from near their coldest point since the ice age to nearly their warmest.

While the new paper is disturbing because it reveals that we’re experiencing weather not seen for 4,000 years, perhaps its most sobering message is that the ice-melting, hurricane-inducing heat can — and will — get worse than this. From The New York Times:

Even if the temperature increase from human activity that is projected for later this century comes out on the low end of estimates, scientists said, the planet will be at least as warm as it was during the warmest periods of the modern geological era, known as the Holocene, and probably warmer than that. …
[Penn State climate scientist Michael E.] Mann pointed out that the early Holocene temperature increase was almost certainly slow, giving plants and creatures time to adjust. But he said the modern spike would probably threaten the survival of many species, in addition to putting severe stresses on human civilization.
“We and other living things can adapt to slower changes,” Dr. Mann said. “It’s the unprecedented speed with which we’re changing the climate that is so worrisome.”